“The Arabic word siddiq is in the superlative form, and refers to a person who is so absorbed in the truth that nothing of his inner self remains. Such a one adheres to rectitude of the highest level, and is a sincere lover of the truth. It is at this point that one is referred to as a siddiq. This is such a station that when a person reaches it, they gather within themselves all forms of truth and rectitude, and begin to draw them in. Just as a burning glass concentrates and draws in the rays of the sun, in the same way a siddiq attracts towards themselves the excellences of truth (sadaqat).”
(Malfuzat [English], Vol. 2, pp. 79-80)